Sprinkler systems for turf irrigation are well known. Typical systems include a plurality of valves and sprinkler heads in fluid communication with a water source, and a centralized controller connected to the water valves. At appropriate times the controller opens the normally closed valves to allow water to flow from the water source to the sprinkler heads. Water then issues from the sprinkler heads in predetermined fashion.
There are many different types of sprinkler heads, including above-the-ground heads and “pop-up” heads. Pop-up sprinklers, though generally more complicated and expensive than other types of sprinklers, are thought to be superior. There are several reasons for this. For example, a pop-up sprinkler's nozzle opening is typically covered when the sprinkler is not in use and is therefore less likely to be partially or completely plugged by debris or insects. Also, when not being used, a pop-up sprinkler is entirely below the surface and out of the way.
The typical pop-up sprinkler head includes a stationary body and a “riser” which extends vertically upward, or “pops up,” when water is allowed to flow to the sprinkler. The riser is in the nature of a hollow tube which supports a nozzle at its upper end. When the normally-closed valve associated with a sprinkler opens to allow water to flow to the sprinkler, two things happen: (i) water pressure pushes against the riser to move it from its retracted to its fully extended position, and (ii) water flows axially upward through the riser, and the nozzle receives the axial flow from the riser and turns it radially to create a radial stream. A spring or other type of resilient element is interposed between the body and the riser to continuously urge the riser toward its retracted, subsurface, position, so that when water pressure is removed the riser will immediately proceed from its extended to its retracted position.
The riser of a pop-up or above-the-ground sprinkler head can remain rotationally stationary or can include a portion which rotates in continuous or oscillatory fashion to water a circular or partly circular area, respectively. More specifically, the riser of the typical rotary sprinkler includes a first portion which does not rotate and a second portion which rotates relative to the first (non-rotating) portion.
As shown in FIG. 1, the rotating portion of a rotary sprinkler riser 10 typically carries a nozzle 12 at its uppermost end. The nozzle 12 throws at least one water steam outwardly to one side of the nozzle assembly 14. As the nozzle assembly 14 rotates, the water stream travels or sweeps over the ground.
The non-rotating portion of a rotary sprinkler riser 10 typically includes a drive mechanism 16 for rotating the nozzle. The drive mechanism 16 generally includes a turbine 18 and a transmission 20. The turbine 18 is usually made with a series of angular vanes 22 on a central rotating shaft (not shown) that is actuated by a flow of fluid subject to pressure. The transmission 20 consists of a reduction gear train (not shown) that converts rotation of the turbine 18 to rotation of the nozzle assembly 14 at a speed slower than the speed of rotation of the turbine 18.
During use, as the initial inrush and pressurization of water enters the riser 10, it strikes against the vanes 22 of the turbine 18 causing rotation of the turbine 18 and, in particular, the turbine shaft. Rotation of the turbine shaft, which extends into the drive housing 24, drives the reduction gear train that causes rotation of an output shaft located at the other end of the drive housing 24. Because the output shaft is attached to the nozzle assembly 14, the nozzle assembly 14 is thereby rotated, but at a reduced speed that is determined by the amount of the reduction provided by the reduction gear train.
With such sprinkler systems, a wide variation in fluid flow out of the nozzle can be obtained. If the system is subject to an increase in fluid flow rate through the riser, the speed of nozzle rotation increases proportionally due to the increased water velocity directed at the vanes of the turbine. In general, increases or decreases in nozzle speed can adversely affect the desired water distribution.
In view of the above, there is a need for an improved rotary sprinkler system for both above-the ground and pop-up rotary sprinkler systems. In particular, it is desirable that the rotary sprinkler system provides a consistent and predictable watering pattern and volume. In addition, the rotary sprinkler system should also be configured to prevent excessive wear on the rotating parts of the system. Furthermore, it is desirable that the rotary sprinkler system controls the rate of rotation of the nozzle. More particularly, it is desirable that the rotary sprinkler system keeps the rate of nozzle rotation relatively constant.